There has been considerable progress in our understanding of inflammation-, tissue-, and microenvironment- selective leukocyte trafficking and its role in immune responses and inflammation. Many adhesion and chemoattractant receptors and their ligands that regulate leukocyte migration have been defined. Their combinatorial use establishes trafficking programs that correlate with and help define the functional specialization of leukocyte subsets. Recent discoveries of traffic modulators, including specialized lipids, enzymes and signaling molecules continue to reveal additional layers of regulation. New imaging techniques provide unprecedented glimpses of migratory dynamics and cell-cell communication in situ. Clinical trials are testing the efficacy of pharmacologic modulation of leukocyte traffic in autoimmune and inflammatory diseases. This program gathers experts in the physiology and molecular biology of leukocyte trafficking to discuss the latest developments in the field and to develop strategies for applying these insights to understanding and manipulating immune responses in vivo. Key topics include: (1) novel technological advances and insights in trafficking research including advances in imaging technologies which are having a major impact on our understanding of immune responses; (2) emerging studies demonstrating that many trafficking molecules (defensins, mucosal chemokines, and cathelicidin family attractants) play roles not only as attractants for antigen presenting and immune cells, but also as direct anti-microbial agents thus bridging the innate and adaptive immune responses; (3) advances in understanding the regulation of T cell and plasma cell homing to the body's specialized surfaces, and the differential effects of routes and modes of vaccination on immune responses; (4) mechanistic insights into leukocyte trafficking in diseases as diverse as multiple sclerosis and atherogenesis; and (5) structural insights into the molecular determinants of integrin and lectin-based adhesion.